1. Field of the Invention
This invention relates to a code system using, for example, a thermo-elastic martensite alloy as a temperature-resistance conversion element and to a hard lock device for use in the code system.
The code system and the hard lock device in accordance with the present invention may be applied to an arbitrary application where secrecy is a requisite. For instance, the present invention may be applied to an access circuit to a computer program which must be kept secret, a lock circuit of a door for a secret entrance, an access circuit to a magnetic disc or optical disc, identification cards whose applications are equivalent to those of IC cards and magnetic cards, and so forth.
2. Prior Art Description
Most of the conventional code circuits or lock systems use softwares and are disadvantageous in that the softwares can be decoded by a trial-and-error method. Lock systems relying upon hardwares are mostly of a mechanical or electromagnetic type, and it is difficult to make such systems in small sizes. In addition, there is an inherent limit to the number of combinations of the codes.
Furthermore, since the conventional code circuits consists mainly of solid semiconductive elements such as ICs and LSIs, the code data and the like are likely to be destroyed by external static electricity or magnetism.